Plug for electrical switch-boards



(No Mmm.)H

H. WY. LELAND.

PLUCPCR ELECTRICAL SWITCH BOARDS. No. 258,931. Patented vJune 6, 1882.

UNITEDYA STATES HARRY W. LELANIL'OF SOUTH FRAMINGHAM, ASSIGNOR TO HIMSELF AND PATENT JOEL O. CLARK, OF FRAMINGHAM, MASSACHUSETTS.

PLUG FOR ELECTRICAL SWITCH-BOARDS.

SPECIFICATION forming part of Letters Patent No. 258,931,'dated .Tune 6, 1882.

Application tiled January 3, 1882. (No model.)

To lall whom it may concern Be it known that I, HARRY W. LELAND,of South Framingham, in the county of Middlesex and State of Massachusetts, have invented certain Improvements in Plugs for Switch- Boards, ot' which the following is a specication.

This invention relates to electrical connecting or looping-in plugs employed in telephonie ex- Io changes and central offices to loop in or connect the operators telephone for the purpose of listening to or answering a call from a subscriber, or to ascertain it' conversation has ceased, or for any otherpurpose when the operator desires to connect his telephone with the circuit of one or more subscribers. i

The invention has for its object to provide a plug whereby the above-mentioned operations may be performed, and also whereby when the 2o plug is inserted into the circuit of one or more subscribers for listening or talking purposes the telephone and other looped-in or connected apparatus may be cut out from said circuit and electric currents sent to line for signalingpurposes. p

To this end my invention consists in the provision upon a plug of the ordinary construction of one or more spring-keys, back contacts, and anvils or terminals adapted to connect 3o one or both of the metallic plates of the plug either with the operators telephone or with current-sending apparatus, one of said connectionsbeing automatically effected by the pressure of thel spring-key and the other by pressure on said key of the opcratorshand holding the plug, as l will now proceed to describe. Ot' the accompanying drawings, forming a part ofthis specification, Figures 12h and 1l represent respectively a longitudinal section and 4o plan View of a plug embodying my invention. Figs.2 and 3 representdiagralns showing the connections therewith.

In carrying out my invention I construct a plug, as usual, of a piece of insulating material, B, having upon its opposite sides plates ab of conducting metal, connected to which are Wires leading to the telephone and other apparatus connected or looped into circuit. In my improvemntone or both of said plates are formed in two lengths, one of which is a spring-key,c, 5o

resting normally against a back contact, d, said back contact being connected to a wire leading tothe telephone. In case the plug is inserted between two subscribers, and it is desired to send electric Vcurrents to only one, the opposite conducting-plateis connected directly by means of a wire to the opposite side of the telephone. So normally the looped-in circuit will be through one plate, its key and back contact, through the telephone back through 6o the other connecting-plate; but when the operator desires -to 'signal the subscriber and presses the key upon its anvil the circuit will be from ground through currentgenerating apparatus, galvanic or ma gueto, through said key to subscribers line, as shown in Fig. 2. By'releasing the key the circuit is immediately restored through the telephone and other apparatus.

When the operator desires for any reason 7o to send a signaling-current to two subscribers a plug such as shown in Fig.3 is used,in which two ot' the above-described keys are used, one on each side 0t` the plug. The normal circuits in this case will be through the back contacts ot' the keys, and when both keys are pressed down onto their anvils thetelephone is cut out and the generating apparatus looped in.

Referring more specitically to the drawings, B represents the insulating material or body 8o of the plug-such as hard rubber formed into the required shape.

a is a plate, of brass or other conducting material, secured to the body B.

b is a plate of brass, also secured to the body 8 5 B at that end of the plug which is formed for insertion into the subscribers circuit. The opposite end ofthe plate b terminates in a springkey, c, which normally rests against a back:

contact, d. 9o

c is an anvil or terminal on the body B, arranged so that the free end of the key c can come in contact with it when the key is displaced or pressed inwardly. The anvil or terminal c' is connected by a wire, e, with amag- 95 neto-generator, M Gr, or with a battery. The back contact, d, isconnected by a wire, g, with a transmitter, T, and the operators telephone,

5 ranged in a circuit with two subscribers, the normal circuit being from subscriber No. l

through plate 11, key c, and back contact, d, transmitter and receiver a to subscriber2. The same figure shows the connection from anvil c 1o of the plug through a magneto-generator, M

G, to the ground. By pressing the key upon its anvil the transmitter and receiver are disconnected and a circuit formed to ground, whereby magneto signaling-currents can be sent to line. It will be understood that by reversin g the plug electric currents can be sent to the other subscriber.

When signals are to be sent to both subscribers the form of plug shown in circuit in Fig. 3

2o is used. In this form the plateahasaspringkey, c, and a back contact, d, which is insulated t'rum the back contact of .the other key. The circuit is normally through the plates a b and back contacts, d, to telephone, and when 2 5 signal-currents are to be sent both keys are depressed upon their anvils, thus looping in au electric generating apparatus and sending currents to both subscribers, or to either part ofthe line-circuit in which the plugis inserted. The key c virtually takes the place of the independent key usually employed to connectthe plu geither with the listenin g-telephone or with the current-sendin g apparatus, said key being at a distance from the plug, so that it 3 5 cannot be operated by the hand that holds the plug. Itis obvious that by locating a key performing the saine function directly on the plug the key can be much more conveniently operated.

I claimy l. Aswitch-board plug ofthe class described, supporting a back contact, a terminal or anvil, and a spring-key, said parts being connected respectively with the operators telephone, with a generator or battery, and with one of the metal plates of the plug, whereby the operator is enabled to manipulate thekey and niake and break the usual connections with the same hand that holds the plug, as set forth.

2. A switch-board plugof the class described, supporting one or more back contacts, one or more terminalsoranvils andoneormorespriugkeys, said parts being connected respectively with the operators telephone, a battery or generator, and one or both of the metal plates of the plug, whereby the operator is enabled to make and break the usual connections with the same hand that holds the plug, and when two back contacts, spring-keys, and terminals are provided the operator is enabled to connect both of the metal plates ot' the plug with a generator or battery, and thereby send currents to both parts of a line-circuit into which the plug is inserted, as set forth.

Inv testimony whereof I have signed my name to this specification, in the presence ot'two subscribing witnesses, this 20th day of December, A. D. 1881.

HARRY WALTER LELAND.

Witnesses:

J AMEs W. THOMSON, GEORGE E. CU'rLER. 

